In the case of surgical interventions in the region of the throat of a patient, such as, in particular, during thyroid surgery, there is the risk of injuring the nerves situated in the area of the operation, particularly the recurrent laryngeal nerve, which leads to voice disorders, a loss of voice and/or respiration or swallowing ailments in the patient. There even is a danger to the life of the patient if both sides of the laryngeal nerve branching out of the vagus nerve are injured during goiter operations.
As a result of using functional monitoring of nerves during the operation, it is possible to largely disable this most commonly occurring and dangerous complication even during thyroid surgery, namely injury to the recurrent laryngeal nerve, which is also referred to as recurrent laryngeal paralysis. Whereas use was previously made of intermittent neuro-monitoring by the operator if a nerve at risk was identified and of checking the nerve function, a continuous monitoring method was proposed in the more recent past, in which an electrode is applied for the duration of the operation to the nerve to be monitored, by means of which the nerve is continuously excited or excited at short intervals without manual activity of the operator, and the response signal following this is derived at the target muscle, namely the vocal cords of the patient, and displayed to the operator via a suitable display instrument. In order to be able to determine the response signal at the vocal cords of the patient, a contact electrode that can be brought into contact with the vocal cords is required. To this end, EP 0 438 863 A1 proposes a discharge system on an endotracheal tube, in which two wires are applied opposite to one another and parallel to the tube axis on the tube part, each wire of which should capture the electric activity of respectively one of the two vocal cords. However, reliable discharging is not possible as a result of this because the contact between the vocal cords and the wire electrodes can be lost even in the case of a slight rotation or movement of the tube, and so there is a threat of lesion of the nerve located in the region of the operation and, more particularly, a continuous neuro-monitoring using the known tube cannot reliably be ensured.
Even if the tube electrodes provided on the right-hand and left-hand side of the tube part in the case of known tubes are equipped with a larger contact surface, areas that cannot capture the electric activity of the vocal cords still remain between the two contact electrodes. If the tube part is not placed correctly during intubation, it may be the case that contact between the electrodes and the vocal cords cannot be ensured even in the case of tubes with relatively broad contact electrodes, and so it is no longer possible to measure any signals, which significantly increases the risk of nerve injury as a result of false-negative signal responses.